Recycling of post consumer and industrial material requires that composite materials be sorted and separated according to color, composition, shape, size, or any of several criteria. Such sorting has traditionally been done manually, wherein sorters visually identify objects to be sorted, and transfer them from one conveyer belt to another running parallel to the first. This is labor intensive and expensive. Automated systems have been developed to replace this traditional hand sorting. In such systems, materials are identified by conventional optical scanner and are transferred from a first conveyer by means of a mechanical or pneumatic force to a second conveyer. Such systems typically are imprecise in their sorting, allowing materials to be mixed, which must then be resorted before pelletization. This lack of precision is due both to the optical scanning mechanism, and the imprecise mechanical and pneumatic sorting mechanism.
Known optical sorting techniques carry materials on a conveyor or vibratory deck and then rely on air jet propulsion methods and or finger push methods that lift or push desired picked materials past an outboard barrier. Unselected items typically fall off the end of the optics conveyor or shaker deck and often dropped on a conveyor below that would transport that material to another optical system where the process occurs again. The selected ejected items that have been propelled either land on another belt or vibratory conveyor and deposited in a holding bunker often with some type of post sorting to qualify the material is correctly identified. Such a system requires extensive room, both horizontally and vertically to allow for conveyers and dropping of the materials.
What is needed therefore is a means for automated sorting heterogeneous material with high degrees of precision.